The overall objectives are the development and perfection of isotope techniques to produce a clinically applicable diagnostic method for Deep Vein Thrombosis, and to test the reliability of two other previously developed methods (Doppler flow and isotope venograms). The goals of this first year were 1) to establish an in vitro model (Chandlier Loop) for testing thrombus labelling characteristics of different radio chemicals and pharmaceutical material; 2) to test the safety and reliability of in vivo thrombus labelling of above materials; 3) to test the safety and applicability of labelling clinically diagnostic thrombi in patients; 4) to confirm and improve the previously developed techniques of ultrasound and isotope venographic methods in patients. Our goals for the coming year are: a) A comparative stability study of the compounds labelled with the various iodines; b) Perform biological half-life and distribution studies in animals to ascertain that the labelling procedure has not altered the biological availability of the compound; c) To determine the effectiveness of the radiolabelled agents in the localization of clots in the in vitro system, and d) To extend this study to in vivo clot localization in animals using both point counting and scanning techniques; e) To investigate radiolabelling of white blood cells and streptokinase; f) To review and reinvestigate the possibility of labelling the most promising compounds with technetium 99m. g) To study the surface charge on macroaggregated albumin and human albumin microspheres, h) To prepare and qualify control radiopharmaceuticals for human clinical studies; and i) To clarify the significance of "hot spots" in radionuclide venography using chronic canine models versus the present acute model.